1. Field of the Invention
The present invention relates to an improvement in a mounting structure of an antenna device with respect to a roof of an automobile, for example.
2. Description of the Related Art
An on-vehicle antenna device can be installed by mounting an antenna module to a desired position of a vehicle body, for example, a roof or a neighboring place. A helical antenna element is an omni-directional antenna element, and suitable for receiving various signals such as satellite radio broadcasting signals, broadcasting global positioning system (GPS) signals, cellular telephone signals, etc.
The related art is Japanese Patent Publication No. JP-A-10-22718.
In the above described on-vehicle antenna device, in order to remove an output of the antenna element, it is necessary to draw a lead cable into the vehicle and connect it to a receiving apparatus or the like. For this purpose, a hollow base projection is integrally provided on a bottom cover which contains the antenna element. This base projection is inserted into an opening formed in the roof so that the lead cable can be drawn into the vehicle by way of the base projection.
As in the conventional mounting structure described above, it is known that the above described base projection is in a form of a bolt which is integral with the bottom cover, and this bolt is fixed to the roof by tightening it with nuts by way of a washer. In this case, it is necessary to insert the base projection of the bottom cover into the opening formed in the roof from the outside of the vehicle, and to tighten it with nuts by way of the washer from the inside of the vehicle room.
According to such conventional mounting structure, it is necessary to contemporaneously insert the base projection into the opening formed in the roof, and tighten the nuts from the inside of the vehicle room. Therefore, the mounting work has become cumbersome, not only because at least two workers are required, but because a number of steps are required for the mounting work.